The present invention relates to conveyors of the type referred to as xe2x80x9ctubexe2x80x9d conveyors. A tube conveyor uses a continuous conveyor belt which is normally flat. The upper or delivery run of the conveyor on which materials are being moved passes through a housing in the form of a tube, normally, but not necessarily, having a circular cross section. The exact shape and dimensions of the tube and belt are not significant.
Conventional tube conveyors are arranged such that the belt passes over two cylindrical rollers, one at the input end and the other at the output end of the conveyor. Typically, but not necessarily, the input roller is an idler roller; and the output roller is driven by a motor, so it is referred as the drive roller. The input roller could be driven, however, and the output roller could be an idler.
The continuous or endless conveyor belt is flat, of course, when passing over the rollers and it is flat in the return run between the drive roller and the input roller. However, in the delivery run (when the conveyor is transporting material from the input roller to the output roller) the conveyor belt passes through the tubular housing or simply xe2x80x9ctubexe2x80x9d (a term which is intended to be broadly construed) and to include all equivalent curved cross sections).
Before entering the tube, the edges of the conveyor belt begin to curve gradually upward, typically from the point at which it leaves the input roller. While the conveyor belt passes through the tube, the edges of the belt are turned upwardly and the belt is curved to conform to the shape of the tubular housing. Material on the conveyor forces the belt into contact and conformation with the lower interior surface of the tubular housing. As the belt leaves the tubular housing it flattens out in smooth transition until it is in wrapping engagement with the drive roller.
Two problems have arisen with tube conveyors of the type described. One problem is that there is a tendency for materials, particularly granular or particulate material such as seed, sand, gravel or the like, to spill off the edges of the conveyor belt in the transition region as the belt leaves the tubular housing and flattens out over the drive roller. In particular, where the conveyor passes over the output or drive roller, the belt is flat, and there is a tendency (caused in part by a vibrating motion of the drive roller and also because the belt becomes flat while the materials are in a heap) for the material being conveyed to roll off the conveyor before being delivered, as the belt is being moved over the output drive roller.
A second problem exists with tube conveyors of this type in that in a conventional arrangement, the frictional drive force on the belt induced by the drive roller is uneven across the length of the roller (i.e., the width of the belt). Uneven force on the belt at this location causes uneven wear on the belt, and loss of friction between the roller and belt, thereby decreasing the useful life of the belt and diminishing its ability to convey material reliably.
The present invention addresses the first problem mentioned above by incorporating adjacent the drive roller, a pair of side bearing mount plates (sometimes called xe2x80x9csaverxe2x80x9d plates) which extend vertically and perpendicular to the axis of the drive roller. The saver plates are mounted to the sidewalls of the transition housing and bearing mounts for the roller are mounted to the saver plates so that the saver plates are positioned adjacent the output roller even if the output roller is adjusted in position.
A curved baffle, fixed to the saver plate of each side wall, is located so that it extends into a recess on the adjacent or opposing side of the output roller. Thus, the curved baffle is nested within the side of the output roller so that the conveyor belt overlaps the innermost edge of the curved baffles. The curvature of the baffles conforms to the curvature on the lateral recess within the output roller so that any material which would otherwise tend to fall down between the roller and the side walls is nevertheless delivered to the output chute at a location very close to the delivery end of the output roller.
The problem of uneven force on the conveyor belt mentioned above is addressed by placing the uppermost surface of the drive roller at a location approximately along a plane extending parallel to the upper edges of the belt while the belt is in the tubular housing. In other words, whether the tubular housing is inclined or horizontal, the edges of the curved conveyor belt inside the tubular housing, define a plane. That plane, which is referred to as the Adjustment Plane, is parallel to the axis of the tubular housing. Thus, if the tubular housing is horizontal, the Adjustment Plane is also horizontal. The Adjustment Plane assumes the angular orientation of the axis or center of the tubular housing. By extending this plane outwardly, and adjusting the upper edge of the drive roller to align with the Adjustment Plane, we have found that the force on the conveyor belt exerted by the drive roller is substantially equal across the width of the belt as it passes over the drive roller, thereby improving performance and increasing the life of the conveyor belt.
Other features and advantages of the present invention would be apparent to persons skilled in the art from the following detailed description of a preferred embodiment accompanied by the attached drawing wherein identical reference numerals will refer to like parts in the various views.